1754-0429-1-11 1754-0429 Research article <p>Synthesis, Infra-red, Raman, NMR and structural characterization by X-ray Diffraction of [C<sub>12</sub>H<sub>17</sub>N<sub>2</sub>]<sub>2</sub>CdCl<sub>4 </sub>and [C<sub>6</sub>H<sub>10</sub>N<sub>2</sub>]<sub>2</sub>Cd<sub>3</sub>Cl<sub>10 </sub>compounds</p> Chaabane Iskandar chaabane.iskandar@yahoo.com Hlel Faouzi faouzihlel@yahoo.fr Guidara Kamel kamelguidara@yahoo.fr

Laboratoire de l'état solide, Faculté des Sciences de Sfax, B. P. 802, 3018 Sfax, Tunisia

 PMC Physics B 1754-0429 2008 1 1 11 http://www.physmathcentral.com/1754-0429/1/11 10.1186/1754-0429-1-11 0805.1804v1 09 11 2007 08 4 2008 08 4 2008 2008 Chaabane et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The synthesis, infra-red, Raman and NMR spectra and crystal structure of 2, 4, 4-trimethyl-4, 5-dihydro-3H-benzo [b] 14 diazepin-1-ium tetrachlorocadmate, [C12H17N2]2CdCl4 and benzene-1,2-diaminium decachlorotricadmate(II) [C6H10N2]2Cd3Cl10 are reported. The [C12H17N2]2CdCl4 compound crystallizes in the triclinic system (P1¯ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaGqaaiab=bfaqnaanaaabaGaeGymaedaaaaa@2D26@ space group) with Z = 2 and the following unit cell dimensions: a = 9.6653(8) Å, b = 9.9081(9) Å, c = 15.3737(2) Å, α = 79.486(1)°, β = 88.610(8)° and γ = 77.550(7)°. The structure was solved by using 4439 independent reflections down to R value of 0.029. In crystal structure, the tetrachlorocadmiate anion is connected to two organic cations through N-H...Cl hydrogen bonds and van der Waals interaction as to build cation-anion-cation cohesion. The [C6H10N2]2Cd3Cl10 crystallizes in the triclinic system (P1¯ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaGqaaiab=bfaqnaanaaabaGaeGymaedaaaaa@2D26@ space group). The unit cell dimensions are a = 6.826 (5)Å, b = 9.861 (7)Å, c = 10.344 (3)Å, α = 103.50 (1)°, β = 96.34 (4)° and γ = 109.45 (3)°, Z = 2. The final R value is 0.053 (Rw = 0.128). Its crystal structure consists of organic cations and polymeric chains of [Cd3 Cl10]4- anions running along the [011] direction, in the [C6H10N2]2Cd3Cl10 compounds hydrogen bond interactions between the inorganic chains and the organic cations, contribute to the crystal packing.

PACS Codes: 61.10.Nz, 61.18.Fs, 78.30.-j

1. Introduction

The synthesis of low-dimensional mixed inorganic-organic materials enables both the inorganic and the organic components on the molecular scale to be optimised and thus to exhibit specific properties, such as electronic, optical, thermal and catalytic 12. Among halometallates (II), chlorocadmates (II) have been of special interest for their structural flexibility. They can occur as simple tetrahedral anions CdX42- or form the backbone of chain polymers. This is due to the fact that the Cd2+ ion, being a d10, exhibits a great variety of coordination numbers and geometries, depending on crystal packing and hydrogen bonding, as well as halide dimensions 345678. Although two-dimensional polymeric chlorocadmates (II) have been widely studied, much less is known about one dimensional linear chain compounds. The major difficulty concerns the fact that the structural possibilities of bidimensional chlorocadmates(II) are somewhat restricted with respect to monodimensional ones, which present a panoply of different structural arrangements. A wide variety of stoichiometries belong to this class of compounds, including [CdCl3], [Cd3Cl8], [Cd2Cl5], [Cd2Cl6], [Cd2Cl7], [Cd3Cl7], [Cd3Cl10], [Cd5Cl14], [CdCl3(OH2)], [Cd2Cl5(OH2)], [Cd2Cl6(OH2)2], [Cd2Cl7(OH2)] and [Cd5Cl12(OH2)2] which makes the crystal chemistry of chlorocadmates (II) extremely diverse and complex. Common features of all these compounds are the invariable presence of octahedral (CdCl6) and/or [CdCl5(OH2)] units in the anhydrous and hydrated species, respectively. Ionized in some different ways, such as sharing triangular faces, edges or vertexes, giving rise to infinite chains usually running parallel along a crystallographic axis. A network of hydrogen bonding, involving organic cations generally connects the columnar stacks of chains together and stabilizes the whole crystal structure 910111213141516.

In the present paper we report on the synthesis, the structural and spectroscopic characterizations of the both [C6H10N2]2Cd3Cl10 and [C12H17N2]2CdCl4 compounds.

2. Experimental

2.1. Preparation of [C12H17N2]2CdCl4 and [C6H10N2]2Cd3Cl10 compound

[C12H17N2]2CdCl4 sample (denoted 1) was prepared by mixing the organic compound 1,2-phenylenediamine, dissolved in acetone, with CdCl2, dissolved in hydrochloric acid solution (1 M), in molar ratio 2:1. By slow evaporation at room temperature, yellow crystals suitable for X-ray single crystal analysis were obtained.

Schematically the reaction proposed in order to justify obtaining [C6H10N2]2Cd3Cl10 sample is shown in figure 1.

<p>Figure 1</p>

Schematically the reaction proposed in order to justify obtaining [C12H17N2]2CdCl4 sample

Schematically the reaction proposed in order to justify obtaining [C12H17N2]2CdCl4 sample.

[C6H10N2]2Cd3Cl10 (denoted 2) sample was prepared by mixing CdCl2, dissolved in hydrochloric acid solution (1 M), and the organic compound 1,2-phenylenediamine, in molar ratio 2:1. By slow evaporation at room temperature, red crystals suitable for X-ray single crystal analysis were obtained.

Schematically the reaction proposed in order to justify obtaining [C6H10N2]2Cd3Cl10 sample is shown in figure 2.

<p>Figure 2</p>

Schematically the reaction proposed in order to justify obtaining [C6H10N2]2Cd3Cl10 sample

Schematically the reaction proposed in order to justify obtaining [C6H10N2]2Cd3Cl10 sample.

2.2. Analysis

The infra-red spectrum was recorded in the 400–4000 cm-1 range with a Perkin-Elmer FT-IR 1000 spectrometer using samples pressed in spectroscopically pure KBr pellets.

The Raman spectrum of [C12H17N2]2CdCl4 and [C6H10N2]2Cd3Cl10 samples were recorded respectively on a Kaiser Optical System spectrometer model-Hololab 5000R in the region 70–3500 cm-1 and HR 800 spectrometer in the region 150–2000 cm-1.

For both compounds 111Cd CP-MAS NMR spectra were measured on powdered sample at 63.648 MHz (7.1 T) with Bruker WB 300 MAS FT-NMR spectrometer. A single pulse sequence was used for all the measurements. The acquisition parameters for compound 1 and 2 were as follows; a 10.5 μs pulse length, 5.0 s pulse delays and 512 and 1024 scan per spectrum respectively. Samples in cylindrical zirconia rotors were spun at spinning rates at 4 KHz and 11 KHz respectively. Chemical shifts were referenced to Cd(ClO4)2 aqueous solution at 0 ppm.

2.3. Crystallographic studies

For compound 1 (0.58 mm × 0.38 mm × 0.25 mm) and compound 2 (0.57 × 0.4 × 0.3 mm3) prismatic crystals were selected by optical examination and mounted on an Enraf-Nonius CAD4 four-circle diffractometer. For both compound 1 and 2 the unit-cell parameters were determined from automatic centering of 25 reflections (12 < θ < 15° and 11 < θ < 16° respectively) and refined by least-squares method. Intensities were collected with graphite monochromatized Mo Kα radiation, using ω/2θ scan-technique.

Two reflections were measured every 2 hrs as orientation and intensity control. No absorption corrections were made for compound 1 and an empirical absorption correction was applied for compound 2 using a method based upon ABSDIF data (transmission range of 0.1611–0.4206). The both structures were solved by Patterson methods, using SHELXS-86 17 in the space group P1¯ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaGqaaiab=bfaqnaanaaabaGaeGymaedaaaaa@2D26@. All the refinement calculations were performed with the SHELXL-93 18 computer program. Cd and Cl atoms were first located. The atomic positions of nitrogen, carbon and hydrogen of the organic groups were subsequently found by difference Fourier syntheses. Details of the crystal structure analysis are reported in Table 1.

<p>Table 1</p>

Summary of crystal data, intensity measurements and refined parameters for [C12H17N2]2CdCl4 and [C6H10N2]2[Cd3Cl10] compounds.

Crystal data

Compound 1

Compound 2

Formula Formula weight (g.mol-1)

[C12H17N2]2CdCl4 632.75

[C6N2H10]2Cd3Cl10 455

Color/shape

yellow/parallelepiped

red/parallelepiped

Crystal dimensions (mm3)

0.58 × 0.38 × 0.25

0.57 × 0.4 × 0.3

Crystal system

triclinic

triclinic

Space group

P 1 ¯ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaGqaaiab=bfaqnaanaaabaGaeGymaedaaaaa@2D26@

P 1 ¯ MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaGqaaiab=bfaqnaanaaabaGaeGymaedaaaaa@2D26@

Cell parameters from 25

12 < θ(°) < 15

11 < θ° < 16

a = 9.687 (8) Å,

a = 6.826 (5)Å,

b = 9.912 (9) Å,

b = 9.861 (7)Å

c = 15.40 (2) Å

c = 10.344 (3)Å

α = 79.4 (1)°,

α = 103.50 (1)°

β = 88.73 (8)°

β = 96.34 (4)°

γ = 77.82 (7)°

γ = 109.45 (3)°

V = 1420 Å3

V = 624.8 (8) Å3

Z = 2, μ = 1.164 mm-1

Z = 2, μ = 3.609 mm-1

Intensity measurements

Temperature (K)

293(2)

293(2)

Radiation, λ (Å), monochromator

MoKα, 0.71069, graphite plate

MoKα, 0.71069, graphite plate

Scan angle (°)

0.8 + 0.35 tg(θ)

0.8 + 0.35 tg(θ)

2θ range (°)

1.5 – 27

2 – 27

Range of h, k, l

-12→12, -2→12, 0→19

-8→8, -12→12, -13→13

Standards reflections

(6 4 0) and (2 6 0)

(-1 6 1) and (-1 5 1)

Frequency

60 mn

Reflections collected/unique

4541/4439 (Rint = 0.0219)

5436/2718 (Rint = 0.0019)

Structure determination

Absorption correction

wasn't applied

ABSDIF Tmin/max: 0.1611/0.4206

Structure resolution

Patterson methods SHELXS86

Patterson methods SHELXS86

Structure refinement with

SHELXL-97

SHELXL-97

Observed reflections [Fo > 2σ(Fo)]

3823

2371

Refinement

F2 full matrix

F2 full matrix

Refined parameters

435

174

Goodness of fit

1.035

1.565

Final R and Rw

0.029, 0.081

0.053, 0.128

Final R and Rw for all data

0.0378, 0.0864

0.0615, 0.1315

Largest feature diff. map

0.668, -0.453 e Å-3

3.256, -2.636 e Å-3

For compound 1: w = 1/[σ2 (Fo)2 + (0.0315 P)2 + 0 P] where P = [Fo2 + 2 Fc2]/3

For compound 2: w = 1/[σ2 (Fo)2+(0.0507P)2 + 0 P] where P = [Fo2 + 2 Fc2]/3

3. Results and discussions

3.1. Infra-red and Raman spectroscopy

3.1.1 [C12H17N2]2CdCl4 (1)

Figures 3a and 3b show IR and Raman spectra respectively of the reported compound at room temperature. A detailed assignment of all the bands is difficult, but we can attribute some of them by comparison with similar compounds 192021. The assignments of the bands observed in the infrared and Raman spectra of [C12H17N2]2CdCl4 are listed in Table 2.

<p>Figure 3</p>

a: Infrared spectrum of [C12H17N2]2CdCl4

a: Infrared spectrum of [C12H17N2]2CdCl4. b: Raman spectrum of [C12H17N2]2CdCl4.

 <p>Table 2</p>

Infrared and Raman spectral data (cm-1) and band assignments for [C12H17N2]2CdCl4.

IR wavenumbers (cm-1)

Raman wavenumbers (cm-1)

Assignment

74

(CdCl42-) Bend.

78

(CdCl42-) Bend.

117

Rotation (C12H17N2+)

128

Rotation (C12H17N2+)

279

CdCl42- Symmetric stretch

457

460

C = C torsion

713

738

CC torsion

763

756

CH and NH Wagg.

955

953

CH Wagg.

1166

1175

CH and CH3 Bend.

1292

1288

CH and NH Bend., CN Str.

1461

1454

CC and CN Str., CH Bend.

1580

C = C Str.

2931

2926

CH Str.

2963

2957

CH Str.

2978

2985

CH Str.

3026

CH Str. (+)

3030

CH Str. (+)

3160

Asymmetric NH Str. (-)

3208

Asymmetric NH Str. (-)

3313

Symmetic NH Str. (+)

3363

Symmetic NH Str. (+)

Bend., bending; Str., stretching; Wagg., wagging; (-) out-of-plane; (+) in plane.

The principal bands are assigned to the internal modes of organic cation. The C = C bands exhibit torsion vibration at 457 cm-1 in IR and 460 cm-1 in Raman, and stretching vibration at 1580 cm-1 in IR. The bands observed at 763, 955 and 765, 953 cm-1 in IR and Raman respectively are ascribed to CH wagging mode. Those observed at 1166, 1292, 1461 cm-1 and 1175, 1288, 1454 cm-1 in IR and Raman respectively are ascribed to CH bending vibration. The CH stretching vibration are observed at 2931, 2963, 2978 cm-1 in IR and 2926, 2957, 2985 cm-1 in Raman. The bands observed at 3160 and 3208 cm-1 in IR are associated to the asymmetric NH stretching out of plane, those observed at 3313 and 3363 cm-1 in IR are ascribed to symmetric NH stretching in plane.

The bands corresponding to the internal vibrational modes of the (CdCl4) anions: ν1, ν2, ν3 and ν4 appear in the Raman spectral region below 300 cm-1. The intense band observed at 279 cm-1 is assigned to the ν1 mode; while the band observed at 78 cm-1 is assigned to the ν4 mode. Finally, the band appearing at 74 cm-1 is assigned to the ν2 mode.

The infrared and Raman study confirms the presence of the organic group C12H17N2 and the tetrahedral anion CdCl42-.

3.1.2 [C6H10N2]2Cd3Cl10 (2)

FTIR and Raman spectra of [C6H10N2]2Cd3Cl10 (2) have been recorded (see Figure 4a and 4b) at room temperature. A detailed assignment of all the bands is difficult but we can attribute some of them by comparison with similar compounds 19.

<p>Figure 4</p>

a: Infrared spectrum of [C6H10N2]2[Cd3Cl10]

a: Infrared spectrum of [C6H10N2]2[Cd3Cl10]. b: Raman spectrum of [C6H10N2]2[Cd3Cl10].

In IR spectrum, the band observed at ~3500 cm-1 can be attributed to symmetric and asymmetric NH stretching vibrations. The characteristic ν(CH) modes of the aromatic ring are observed as expected in the 3170-2680 cm-1 spectral regions. The bands observed between ~1540 and ~1620 cm-1 are ascribed to C = C stretching mode. The intense band observed at 1490 cm-1 is associated with the vibrations of the C-N-H group mixed with C-C stretching and CH bending. The intense band observed at 1470 cm-1 is attributed to C-C and C-N stretching and CH bending vibrations. A very strong band observed at 1310 cm-1 results purely from interaction between the N-H and C-H bending and C-N stretching vibrations. The band observed between 1130 cm-1 and 1240 cm-1 is attributed to CH bending vibrations. The symmetric out of plane CH vibration (CH-wagging) creates a very strong band at 772 cm-1 whereas weak bands observed at 861 cm-1 and 876 cm-1 were attributed to CCC bending and C-N stretching. The medium bands observed in the region between 519 and 581 cm-1 are commonly attributed to ring torsion. The strong band observed at 443 cm-1 is ascribed to C = C torsion vibration. These vibrational absorptions are listed in Table 3.

<p>Table 3</p>

Infrared and Raman spectral data (cm-1) and band assignments for [C6H10N2]2[Cd3Cl10] sample.

IR wavenumbers (cm-1)

Raman wavenumbers (cm-1)

Assignment

158

Cd-Cl Bend.

180

Cd-Cl (equatorial) Bend.

443

C = C torsion

503

519

592

aromatic ring torsion

581

606

668

CCC Bend.

688

743

CC torsion

752

772

CH and NH Wagg.

833

CH Wagg.

861

NH Wagg.

876

CH Wagg.

1070

1044

CC Str., CH and CCC Bend.

1100

1130

1155

CH Bend.

1140

1165

1240

1247

1310

1373

CC and CN Str.

1470

1400

1490

CH Bend., CC and CN Str.

1540

1505

C = C Str.

1580

1545

1620

1575

2920

CH Str.

3500

Asymmetric and Symmetic NH Str.

Bend., bending; Str., stretching; Wagg., wagging;

The bands corresponding to the internal vibrational modes of the (CdCl6) anions appear in the Raman spectral region below 300 cm-1. The intense band observed at 158 cm-1 is assigned to the Cd-Cl bending; while the band observed at 180 cm-1 is assigned to the Cd-Cl (equatorial) bending 22. These vibrational absorptions are given in Table 3.

The infrared and Raman study confirms the presence of the organic group C6H10N2 and the octahedral anion CdCl6.

3.2. NMR measurements

The 111Cd MAS NMR spectra of compound 1 and 2 are shown respectively in Figures 5a and 5b. The spectrum of compound 1 is composed of one broad peak and two spinning side bands. The δiso value is equal to 468.01 ppm indicating that CdCl42- tetrahedral is present in the sample 23. Based on the 111Cd MAS NMR measurements of several chlorocadmate crystals with known structures, Sakida et al. have shown that the δiso value for the CdCl6 octahedra is equal to 183 ppm 24. Hence, it may be concluded that the compound 2 is composed of CdCl6 octahedra alone. The δiso value of Cd(1)Cl6 octahedra is much smaller than that of Cd(2)Cl6. This fact indicates that the octahedral anion-co-ordination around Cd2+ has higher symmetry in the Cd(1)Cl6 octahedra than in the Cd(2)Cl6.

<p>Figure 5</p>

a: Cross polarization 111Cd MAS NMR spectra of [C12H17N2]2CdCl4 compound

a: Cross polarization 111Cd MAS NMR spectra of [C12H17N2]2CdCl4 compound. b: Cross polarization 111Cd MAS NMR spectra of [C6H10N2]2[Cd3Cl10] compound.

3.3. Description of the structures

3.3.1 [C12H17N2]2CdCl4 (1)

Selected inter-atomic distances and angles are given in Tables 4, 5, 6 and 7, respectively.

<p>Table 4</p>

Main inter-atomic distances (Å) in anionic part of [C12H17N2]2CdCl4 and [C6H10N2]2[Cd3Cl10] compounds. (Esd are given in parentheses).

Compound (1)

Compound (2)

Distance (Å) of CdCl4

Distance (Å) of Cd(1)Cl6

Distance (Å) of Cd(2)Cl6

Cd-Cl(1)

2.497(3)

Cd1–Cl3

2.551(1)

Cd2–Cl6

2.519(1)

Cd-Cl(2)

2.501(2)

Cd1–Cl3i

2.551(1)

Cd2–Cl7i

2.583(1)

Cd-Cl(3)

2.423(3)

Cd1–Cl5

2.669(1)

Cd2–Cl3

2.600(1)

Cd-Cl(4)

2.416(2)

Cd1-Cl5i

2.669(1)

Cd2-Cl4

2.694(1)

Cd1-Cl4ii

2.689(1)

Cd2-Cl5iv

2.710(1)

Cd1-Cl4iv

2.689(1)

Cd2-Cl4iii

2.739(1)

 <p>Table 5</p>

Main inter-atomic distances (Å) in cationic part of [C12H17N2]2CdCl4 and [C6H10N2]2[Cd3Cl10] compounds. (Esd are given in parentheses).

Compound (1)

Compound (2)

Distance (Å) of C12H17N2+(a)

Distance (Å) of C12H17N2+(b)

Distance (Å) of C6N2H10

C(11)-C(12)

1.388(6)

C(21)-C(22)

1.383(5)

C1-C6vi

1.387(6)

C(12)-C(13)

1.383(7)

C(22)-C(23)

1.378(5)

C2-C1v

1.367(7)

C(13)-C(14)

1.373(8)

C(23)-C(24)

1.396(6)

C2vi-C5

1.381(8)

C(14)-C(15)

1.356(7)

C(24)-C(25)

1.352(6)

C3-C4

1.367(8)

C(15)-C(16)

1.410(5)

C(25)-C(26)

1.426(4)

C3-C6

1.395(7)

C(16)-C(11)

1.406(4)

C(21)-C(26)

1.415(5)

C4-C5v

1.378(9)

C(11)-N(11)

1.405(5)

C(21)-N(21)

1.430(4)

C1-N1

1.473(6)

N(11)-C(17)

1.482(4)

N(21)-C(27)

1.291(5)

C6-N2

1.460(6)

C(17)-C(171)

1.533(6)

C(27)-C(271)

1.502(5)

C(17)-C(172)

1.511(7)

C(27)-C(28)

1.466(5)

C(17)-C(18)

1.542(5)

C(28)-C(29)

1.551(4)

C(18)-C(19)

1.492(6)

C(29)-C(291)

1.520(6)

C(19)-C(191)

1.467(8)

C(29)-C(292)

1.506(6)

C(19)-N(12)

1.307(5)

C(29)-N(22)

1.485(5)

C(16)-N(12)

1.400(5)

N(22)-C(26)

1.350(5)

-

    symmetry code
: i: -x+1,-y,-z+1; ii: x-1,y,z; iii: -x+2,-y,-z+1; vi: x+1,y,z;

v: -x+2,-y,-z+2; vi: x,y-1,z; vii: x,y+1,z;

 <p>Table 6</p>

Main bond angles (°) in anionic part of [C12H17N2]2CdCl4 and [C6H10N2]2[Cd3Cl10] compounds. (Esd are given in parentheses).

Compound (1)

Compound (2)

Angle (°) of CdCl4

Angle (°) of Cd(1)Cl6

Angle (°) of Cd(2)Cl6

Cl(1)-Cd-Cl(2)

101.81(9)

Cl3-Cd1-Cl3i

180

Cl6-Cd2-Cl7

92.55(4)

Cl(1)-Cd-Cl(3)

108.85(9)

Cl3-Cd1-Cl5

90.46(4)

Cl6-Cd2-Cl3

96.22(4)

Cl(1)-Cd-Cl(4)

110.14(9)

Cl3i-Cd1-Cl5

89.54(4)

Cl7-Cd2-Cl3

96.02(4)

Cl(2)-Cd-Cl(3)

109.78(9)

Cl3-Cd1-Cl5i

89.54(4)

Cl6-Cd2-Cl4

94.15(4)

Cl(2)-Cd-Cl(4)

106.87(8)

Cl3i-Cd1-Cl5i

90.46(4)

Cl7-Cd2-Cl4

166.97(4)

Cl(3)-Cd-Cl(4)

118.13(9)

Cl5-Cd1-Cl5i

180

Cl3-Cd2-Cl4

94.35(4)

Cl3-Cd1-Cl4ii

95.14(3)

Cl6-Cd2-Cl5iv

92.92(4)

Cl3i-Cd1-Cl4ii

84.86(3)

Cl7-Cd2-Cl5iv

85.10(4)

Cl5-Cd1-Cl4ii

84.28(3)

Cl3-Cd2-Cl5iv

170.72(4)

Cl5i-Cd1-Cl4ii

95.72(3)

Cl4-Cd2-Cl5iv

83.41(3)

Cl3-Cd1-Cl4iii

84.86(3)

Cl6-Cd2-Cl4iii

178.10(4)

Cl3i-Cd1-Cl4iii

95.14(3)

Cl7-Cd2-Cl4iii

89.22(4)

Cl5-Cd1-Cl4iii

95.72(3)

Cl3-Cd2-Cl4iii

82.93(4)

Cl5i-Cd1-Cl4iii

84.28(3)

Cl4-Cd2-Cl4iii

84.23(4)

Cl4ii-Cd1-Cl4iii

180

Cl5iv-Cd2-Cl4iii

87.88(3)

 <p>Table 7</p>

Main bond angles (°) in cationic groups of [C12H17N2]2CdCl4 and [C6H10N2]2[Cd3Cl10] compounds. (Esd are given in parentheses).

Compound (1)

Compound (2)

Angle (°) of C12H17N2+(a)

Angle (°) of C12H17N2+(b)

Angle (°) of C6N2H10

C(13)-C(12)-C(11)

121.9(4)

C(23)-C(22)-C(21)

121.7(4)

C2v-C1-C6vi

120.8(5)

C(14)-C(13)-C(12)

120.4(5)

C(22)-C(23)-C(24)

118.8(4)

C1v-C2-C5vii

119.1(4)

C(15)-C(14)-C(13)

119.6(4)

C(25)-C(24)-C(23)

120.0(3)

C3-C4-C5v

120.2(5)

C(14)-C(15)-C(16)

120.9(4)

C(24)-C(25)-C(26)

123.2(3)

C2vi-C5-C4v

120.9(5)

C(12)-C(11)-C(16)

117.1(3)

C(21)-C(26)-C(25)

115.4(3)

C1vii-C6-C3

119.4(5)

N(11)-C(11)-C(16)

120.4(4)

C(22)-C(21)-C(26)

120.8(3)

C1vii-C6-N2

121.7(4)

C(12)-C(11)-N(11)

122.2(3)

C(26)-C(21)-N(21)

124.7(3)

C3-C6-N2

118.8(4)

C(11)-N(11)-C(17)

122.7(3)

C(22)-C(21)-N(21)

114.4(3)

C2v-C1-N1

118.5(4)

N(11)-C(17)-C(171)

110.4(4)

C(27)-N(21)-C(21)

129.3(4)

C6vi-C1-N1

120.7(4)

N(11)-C(17)-C(172)

108.3(3)

N(21)-C(27)-C(271)

117.5(4)

C(172)-C(17)C(171)

109.5(4)

N(21)-C(27)-C(28)

120.1(3)

N(11)-C(17)-C(18)

107.8(2)

C(28)-C(27)-C(271)

122.3(3)

C(172)-C(17)-C(18)

112.6(4)

C(27)-C(28)-C(29)

115.1(3)

C(171)-C(17)-C(18)

108.2(4)

C(291)-C(29)-C(28)

109.7(3)

C(19)-C(18)-C(17)

113.1(3)

C(292)-C(29)-C(28)

109.1(3)

C(191)-C(19)-C(18)

122.7(4)

C(292)-C(29)-C(291)

111.0(3)

N(12)-C(19)-C(18)

117.3(4)

N(22)-C(29)-C(28)

108.9(3)

N(12)-C(19)-C(191)

119.8(4)

N(22)-C(29)-C(291)

113.1(4)

C(19)-N(12)-C(16)

126.5(3)

N(22)-C(29)-C(292)

104.9(3)

N(12)-C(16)-C(11)

120.2(3)

C(26)-N(22)-C(29)

128.6(3)

N(12)-C(16)-C(15)

119.6(3)

N(22)-C(26)-C(21)

129.3(3)

C(11)-C(16)-C(15)

120.0(4)

N(22)-C(26)-C(25)

115.2(3)

-

    symmetry code
: i: -x+1,-y,-z+1; ii: x-1,y,z; iii: -x+2,-y,-z+1; iv: x+1,y,z;

v: -x+2,-y,-z+2; vi: x,y-1,z; vii: x,y+1,z;

The structure can be described by an alternation of organic and inorganic layers stacked in the c direction. The anionic layer is built up of tetrahedra of tetrachlorocadmate CdCl42- sandwiched between two different organic layers. The first one located at z = 0 is formed by C12N2H17+ (a) cations. The second is build up of C12N2H17+ (b) cations observed at z = 1/2 (Figure 6). The benzene rings in cations one and two are not parallel. The angle between them is equal to 77.3 (1)°.

<p>Figure 6</p>

[010] view of the structure of [C12H17N2]2CdCl4

[010] view of the structure of [C12H17N2]2CdCl4. The large empty circles represent nitrogen atoms, the small medium grey circles represent hydrogen atoms and the black circles represent carbon ones. CdCl42- anions are represented by tetrahedra. Hydrogen bonds are represented by broken lines.

The material cohesion is assured by two different interactions:

- The bonding between the organic and inorganic layers is established by three different hydrogen bonds (Cl1...HN21-N21, Cl2...HN12-N12 and Cl2...HN11-N11). The N...Cl distances vary between 3.134 (4) Å and 3.691 (4) Å. We deduce that the hydrogen links are weak (Table 8) 25.

<p>Table 8</p>

Main inter-atomic distances (Å) and bond angles (°) involved in the hydrogen Bonds of [C12H17N2]2CdCl4 compounds. (Esd are given in parentheses).

Cl...H-N

H-N (Å)

Cl...H (Å)

Cl...N (Å)

Cl...H-N (°)

Cl1...HN21-N21(i)

0.74(4)

2.57 (4)

3.306 (4)

171 (3)

Cl2...HN12-N12

0.78(4)

2.37 (4)

3.134 (4)

167 (4)

Cl2...HN11-N11

0.82(4)

2.89 (4)

3.691 (4)

163 (4)

-

    symmetry code
: i: 1-x, 2-y, 1-z.

- The cohesion of the organic layer is obtained by van der Waals interaction between aromatic π-stacking. The separation between the planes of two aromatic cations from adjacent dimeric unit is 4.29 (6) Å 426 (Figure 6).

3.3.1.1 Geometry and coordination of the tetrachlorocadmiate anion

CdCl42- tetrahedron presents a C1 punctual symmetry. The geometrical features of CdCl4 entity are comparable to those found in the Cambridge Structural Database (CSD) for other Cd(II) salts containing isolated [CdCl4]2- tetrahedral anions 27. The range of average Cd-Cl distances is 2.45–2.47 Å. In our case the Cd-Cl distances vary between 2.416(2) and 2.501(2) Å with a mean of 2.459(3) Å (Table 4). The Cl-Cd-Cl angle values are in the 101.81(9)° – 118.13(9)° range with a mean of 109.26(9)° (Table 6). Taking into account these parameters and considering the calculated average values of the Baur distortion indices 28 {ID Cd-Cl = 0.0157(1), ID Cl-Cd-Cl = 0.031(1) and ID Cl-Cl = 0.0157(1)}, we deduce that the CdCl4 tetrahedron is slightly distorted.

3.3.1.2 Geometry and coordination of the organic cations

Ortep representations of C12H17N2+ (a) and C12H17N2+(b) cations showing ellipsoid thermal unrest are shown in Figures 7a and 7b, respectively.

<p>Figure 7</p>

a: Showing the ellipsoid of thermic unrest of carbon and nitrogen atoms at 40% in C12H17N2+(a) cation

a: Showing the ellipsoid of thermic unrest of carbon and nitrogen atoms at 40% in C12H17N2+(a) cation. b: Showing the ellipsoid of thermic unrest of carbon and nitrogen atoms at 40% in C12H17N2+(b) cation.

The C-C distances in the benzene of the first and second cations vary in the ranges 1.356(8)–1.411(2) Å and 1.352(6)–1.426(4) Å respectively (Table 5). The C-C-C angle values in the aromatic ring are in the range 117.1(3)° – 121.9(4)° and 115.4(3)° – 123.2(3)° for the first and second cation respectively (Table 7).

The benzene rings of those cations are distorted and slightly deviated from their medium plane.

The equation of the average plane for the first and second cations are, respectively, 7.11(1) x + 1.70(1) y - 9.96(2) z = 0.66 (3) and 4.55 (1) x - 1.99 (2) y + 11.80 (2) z = 4.91 (2). In the first and second cation, the average deviation of carbon atoms from the ideal aromatic ring is 0.0032 Å and 0.0064 Å, respectively. We deduce that the C12H17N2+(2) cation is more deformed.

3.3.2 [C6H10N2]2Cd3Cl10 (2)

Selected inter-atomic distances and angles are given in Tables 4, 5, 6 and 7, respectively.

The crystal structure of the [C6H10N2]2[Cd3Cl10] compound can be described by an alternation of organic and inorganic layers stacked in the [011] direction. The inorganic layer is built up of an infinite one-dimensional inorganic chain of [Cd3Cl10]n4n- moieties running along the [011] direction (Figure 8). Two types of six-coordinated Cd are observed: Cd(1)Cl6 and Cd(2)Cl6. In the trimer, two Cd(2)Cl6 octahedra generated by a symmetric center share one bridging chlorine atom (C1(4), C1(4')), the Cd(1)Cl6 octahedron shares one bridging chlorine atom (C1(4), C1(3)) with the Cd(2)Cl6 octahedron and another bridging chlorine atom (C1(4), C1(5)) with the Cd(2')Cl6 octahedron (Figure 9). In the same layer, the infinite one-dimensional inorganic chains are connected by C6H10N22+ cations via hydrogen bonding (N-H...Cl) (Table 9). One type of organic cation, C6H10N22+, is observed on both sides of every infinite one-dimensional inorganic chain. Each organic cation orients its NH3 groups towards the inorganic chain in order to form three hydrogen bonds with free chlorine atom of the CdCl6 octahedron and two hydrogen bonds with common chlorine atoms between two types of octahedron.

<p>Table 9</p>

Main inter-atomic distances (Å) and bond angles (°) involved in the hydrogen Bonds of [C6H10N2]2[Cd3Cl10] compounds. (Esd are given in parentheses).

N-H...Cl

H-N (Å)

Cl...H (Å)

Cl...N (Å)

Cl...H-N (°)

N1-HN11... Cl7i

0.923(4)

2.333(6)

3.199(8)

156.3(8)

N1-HN12... Cl6

1.108(6)

2.102(7)

3.122(6)

151.8(7)

N1-HN12... Cl5i

1.108(2)

3.195(4)

3.776(8)

113.5(9)

N1-HN13... Cl6ii

0.826(5)

2.458(4)

3.185(5)

147.3(6)

N2-HN21... Cl5iii

1.011(4)

2.191(6)

3.198(5)

173.7(7)

N2-HN22... Cl5vii

0.751(4)

2.551(5)

3.254(7)

156.5(8)

N2-HN22... Cl4

0.751(3)

3.149(4)

3.548(3)

116.5(4)

N2-HN23... Cl7i

0.992(4)

2.443(5)

3.222(4)

135.1(6)

N2-HN23... Cl7iv

0.992(6)

2.693(6)

3.310(4)

120.6(4)

-

    symmetry code
: i: x+1, y, z; ii: -x+3, -y, -z+2; iii: x+1, y+1, z;

iv: -x+2, -y, -z+1; v: x-1, y-1, z; vi: x-1, y, z; vii: -x+1, -y, -z+1

 <p>Figure 8</p>

[011] view of the structure of [C6H10N2]2[Cd3Cl10] sample

[011] view of the structure of [C6H10N2]2[Cd3Cl10] sample. The large empty circles represent nitrogen atoms, the small medium grey circles represent hydrogen atoms and the black circles represent carbon ones. Cd3Cl104- anions are represented by octahedra. Hydrogen bonds are represented by broken lines.

 <p>Figure 9</p>

Showing the coordination of Cd3Cl104- anions and the ellipsoid of thermic unrest of chlorine and cadmium atoms at 40%

Showing the coordination of Cd3Cl104- anions and the ellipsoid of thermic unrest of chlorine and cadmium atoms at 40%.

From one organic-inorganic layer to other, the cohesion is assured by hydrogen bonding (N-H...Cl) (table 9). Every cation forms three hydrogen bonds with the two layers observed on both sides of its own layer.

3.3.2.1 Geometry and coordination of hexachlorocadmate anion

3.3.2.1.1 Geometry of Cd(1)Cl6

The geometry of the Cd(1)Cl64- anion is shown in Figure 9, and it is apparent that the coordination around the cadmium is slightly distorted from octahedral symmetry, presenting a C2ν punctual symmetry. The base of this octahedron is formed by Cl(3) and Cl(5) chlorine atoms and their symmetry by reversal center. The Cl-Cd-Cl angle values are in the 89.54(4)° – 90.46(4)° range (table 6). The range of Cd-Cl distances is between 2.551(1) and 2.669(1)Å (table 4). The chlorine atom observed in both sides of the tetrahedron base show a longer Cd-C1 bond length (Cd-Cl(4) = 2.689(1)Å). The Cl(4)-Cd-Cl angles with the Cl atom of the octahedron base are in the 84.28(3)°–95.72(3)° range, shown to be slightly distorted from octahedral symmetry.

The Cl-Cd-Cl angles of opposite chlorine atoms about cadmium atom center are planar. In fact, the cadmium ion is located at the center of octahedron.

3.3.2.1.2 Geometry of Cd(2)Cl6

The Cd(2)Cl6 octahedra presents a Ci punctual symmetry. The Cl-Cd-Cl angles between opposite chlorine atoms about the cadmium atom center do not form the ideal octahedral shape. The angle values are in the 166.97(4)–178.10(4)° range, which proves that the cadmium atom is slightly shifted to the center of the octahedral one (table 6). The remainder of the Cl-Cd-Cl angles show a variation of ± 6° in both sides of ideal octahedral shape (90°). The Cd-Cl distances are more dispersed than those observed in the Cd(1)Cl6 octahedra. The range of Cd-Cl distances is between 2.519(1) and 2.739(1)Å (table 4).

3.3.3 Geometry of organic group

The asymmetrical unit contains only one C6H10N22+ grouping (Figure 10). The aromatic ring of the cation is slightly distorted. The carbon atoms show a low distortion compared to the average plan of 0.52Å.

<p>Figure 10</p>

Showing the ellipsoid of thermic unrest of carbon and nitrogen atoms at 40% in C6H10N22+ cation

Showing the ellipsoid of thermic unrest of carbon and nitrogen atoms at 40% in C6H10N22+ cation.

The main geometric features of the organic cation are similar to those commonly observed in hybrid compounds 13. The C-C distances and the C-C-C angles values in the benzene vary in the range 1.367(7)–1.395(7)Å and 119.1(4)–120.9(5)°, respectively (tables 5 and 7).

4. Conclusion

Two new compounds [C12H17N2]2CdCl4 and [C6H10N2]2[Cd3Cl10] have been synthesized using solution methods. The atomic arrangement of the both compounds can be described by alternating layers of organic and inorganic material stacked parallel to the ab plane and according to the [011] direction respectively. The material cohesion for all compounds is assured by two different bonds. The bonding between the inorganic and organic layer is established by N – H...Cl – Cd interaction, and the cohesion of the organic layer is assumed by Van Der Waals interaction between aromatic π-stacking. The inorganic layer for the [C6H10N2]2[Cd3Cl10] compound is constructed from infinite one-dimensional inorganic chains of [Cd3Cl10]n4n- moieties running along the [011] direction, and that for the [C12H17N2]2CdCl4 sample is formed from insulated tetrahedrals [CdCl4]2-. Infrared and Raman spectroscopy and NMR study confirms the presence of organic and inorganic groups for both compounds.

Acknowledgements

We are grateful to Professor Monsour Salem for informative discussion in order to propose a way to justify obtaining the ion 2,4,4-trimethyl-4,5-dihydro-3H-benzo [b] diazepin-1-ium from 1,2-phenylenediamine, in the synthesis of compound 1.

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